1. Field of the Invention
The present invention relates to an image forming apparatus wherein ink is supplied to an electrostatic latent image formed on a surface of an image bearing element to form an ink image, which is then transferred onto a recording medium to form an image thereon and the ink remaining on the surface of the image bearing element after image transfer is removed therefrom by means of a cleaning unit. The image forming apparatus according to the present invention is characterized by the cleaning unit capable of satisfactorily removing the residual ink from the surface of the image bearing element after image transfer.
2. Description of the Related Art
There has been used a conventional image forming apparatus represented by an electrophotographic copier which forms an electrostatic latent image on a surface of an image bearing element, develops the electrostatic latent image, and transfers it onto a recording medium such as paper to form an image thereon.
As an example of the electrophotographic image forming apparatus, there has been known one using a liquid developing agent composed of coloring resin particles (toner particles) dispersed in a liquid carrier to develop an electrostatic latent image.
A typical liquid developing agent used in the electrophotographic apparatus is composed of charged toner particles dispersed in an insulating liquid carrier. Since the toner particles in the liquid developing agent are selectively used as image formation proceeds, it is required to control the concentration of the toner particles in the liquid carrier, which causes the problems of troublesome control of the concentration of the toner particles and easy degradation of the liquid developing agent because, in most cases, the liquid carrier is used repeatedly over several times.
To form an image on a recording medium such as paper for photocopying, the electrophotographic apparatus thus using the liquid developing agent requires an additional device such as a fixing unit for fixing a toner image transferred onto the recording medium, resulting in a complicated and cumbersome apparatus.
There has also been proposed a conventional image forming apparatus as disclosed in U.S. Pat. No. 4,272,599 wherein ink is supplied to an electrostatic latent image formed on a surface of an image bearing element to form an ink image, which is then transferred onto a recording medium to form an image thereon and the ink remaining on the surface of the image bearing element after image transfer is removed therefrom by means of a cleaning unit.
In the case of supplying ink to the electrostatic latent image formed on the surface of the image bearing element and transferring the ink image onto the recording medium to form the image thereon, as described above, ink to be used preferably has a high viscosity to prevent the recording medium from being blurred with the ink and provide a high-quality image.
If such ink with a high viscosity is used, however, the cleaning unit cannot satisfactorily remove the residual ink from the surface of the image bearing element after image transfer, which causes the problems of fogging observed in the formed image and a need for a complicated and high-cost cleaning unit capable of satisfactorily removing the ink from the surface of the image bearing element.